Tag Archives: blood examination

Electrophoresis Test

By @forensicfield

What is Electrophoresis Test?

Electrophoresis is being used for the separation of various enzyme system.

There are two type of electrophoretic method have been recommended for identification of blood stains;-

  • 1] Separation and identification of hemoglobin by electrophoresis, and,
  • 2] Separation and identification of serum proteins by immunoelectrophoresis.

Immunoelectrophoresis is a two‐stage process:

  • 1.} Electrophoresis is conducted, and;
  • 2.} Immunoprecipitation using antibodies against specific proteins.

Resolution is improved by staining the proteins.

The technique is widely used to identify monoclonal immunoglobulins (M‐components) in serum and urine.

It’s Uses In Forensics

It’s a Confirmatory test for blood.

Basis Of The Test

This process involves the separation of Marker Proteins that are found on the surface of red blood cells.

Indication for the Presence of Blood

Electrophoresis  can be used to isolate and compare DNA, Blood proteins and inorganic substances.

How To Perform This Test ?

For Analyzing of Proteins

Drawbacks

The disadvantages are that gels can melt during electrophoresis, the buffer can become exhausted, and different forms of genetic material may run in unpredictable forms.

Watch it🤳, Share it ✌and Subscribe it 👇 : –

Wagenaar’s Test

By @forensicfield

What is Wagenaar’s Test?

This test was discovered by Wagenaar in 1935.

Wagenaar reagent- acetone and Hcl 10% v/v.

It’s Uses In Forensics

It’s a Confirmatory test for blood.

It is also known as Acetone chlor-hemin crystal test.

Indication for the Presence of Blood

When sample goes through wagenaar reagent, it gives brownish rhomboidal crystals under microscope.

How To Perform This Test ?

Drawbacks

Sometimes obtained crystals are difficult to observe.

Watch it🤳, Share it ✌and Subscribe it 👇 : –

Teichmann Crystal Test

By @forensicfield

What is Teichmann Crystal Test?

Dr. Ludwig Karl Teichman discovered a test for detection of blood in 1853. later the test name as Teichmann Crystal Test.

It’s Uses In Forensics

It’s a Confirmatory test for blood.

It is also known as Haematin crystal acid test or haemin test.

It is used in detection of blood from dried stains.

Basis Of The Test

In Teichmann Test hemoglobin converted to haemin crystals which converted to salt in presence of halogen after then rhombic crystals forms.

Indication for the Presence of Blood

It produced Dark brown Color and rhombic shape if blood is present.

How To Perform This Test ?

Drawbacks

Rust and Exposure or combination of these can interfere with the test.

Watch it🤳, Share it ✌and Subscribe it 👇 : –

Examination of Blood in Forensics

By @forensicfield

INTRODUCTION

Blood is a type of biological evidence which is commonly found at the scene of crime.

Blood stains are often found at various types of crime scene, such as homicide, hit and run, assault, child abuse, rape, robbery and burglary. it also uses for DNA extraction and establishes  the paternity test.

Since the discovery of the ABO system by Land-steiner in 1900, knowledge in human blood identification has expanded tremendously.

Composition Of Human Blood

Blood is a mixture of many components:

* Cells

* Enzymes

* Proteins                            

* Water

* Inorganic substances (salts)

Blood contains 2 types of proteins which are-

  • Plasma
  • Corpuscles

The blood cells are of three main types:

  • Red Blood Cells (Erythrocytes)
  • White blood cells (Leucocytes)
  • Platelets (Thrombocytes)

Use of Blood detection in Forensic Science:

Blood is one of the most important biological traces that are often found on the crime scene. Due to valuable information it contains, it is considered to be a very important forensic tool. Analysis of different aspects of bloodstains can contribute to clarify the circumstances under which some violent crimes have been committed. Such crucial information can point criminal investigation in the right direction and help solve the crime. In some cases it can also help with legal determination of criminal offense which can lead to more accurate and more appropriate punishment for the perpetrator. It is very important to determine the sequence of events during the commitment of a violent crime involving blood.

Identification Of Source Of Blood

Foetal blood–  presence of HbF or Alpha Protein.

Blood of Pregnancy and abortion – Chorionic Gonadotropins or or Alkaline Phosphatase.

Menstrual blood– Fibrin Content, endometrial tissues.

Venous blood– dark in color, oozes gradually and no spurting.

Arterial – bright red and copious and showed spraying.

Methods For The Identification Of Blood

5 Types Of Blood Test Or Methods Occurred-

  1. Visual / Physical examination
  2. Microscopic examination
  3. Chemical Examination
  4. Spectroscopic Examination
  5. Serological examination
Visual /  Physical Examination

The search for the presence of blood at a crime scene is normally done by close visual examination.  The possibility exists, however, that blood may be present in amounts too little to see with the unaided eye, or that the blood at the scene had been “cleaned up” prior to arrival of the crime scene team. 

Fresh stains – bright in colour, turns to brown and black after some time. Fresh stains soluble in water or in saline

Ante-mortem blood Stains – Removed in scales due to presence of fibrin.

Post-mortem blood stain – changes in powdered on removal.

Microscopic Examination

Fresh blood stain in Microscope  – Erythrocytes and leukocytes.

Microscopic appearance of cells found in a stain extract may reveal other information.

If blood stains in an environment with a higher solute concentrate, water leaves the cell by osmosis and the cells shrink and change shape.

If stains are fresh it is possible to reconstitute the stain and proceed with microscopical identification of cellular components.

Chemical Examination

Preliminary

  1. BENZIDINE TEST
  2. LUMINOL TEST
  3. PHENOLPHTHALEIN (KASTLE – MAYER TEST)
  4. FLUORESCEIN TEST
  5. LEUCOMALACHITE GREEN TEST
  6. COLORIMETRI TEST

Confirmatory

  1. TEICHMANN TEST
  2. TAKAYAMA TEST
  3. WAGENNAR TEST
  4. SPECTROPHOTOMETRY TEST
  5. ELECTROPHORESIS TEST

Watch it🤳, Share it ✌and Subscribe it 👇 : –